The present invention relates to an apparatus for filling a melt into a casting chamber for die casting, having a tundish with an inner volume, wherein the inner volume can be filled with the melt. The invention also relates to a method for filling a melt into a casting chamber for die casting by way of the apparatus.
Modern technology often uses die casting for the series production or mass production of structural parts. In the case of known die-casting methods, in the first instance liquid melt is filled into a casting chamber, in particular by dosing. With the aid of a plunger, the melt in the casting chamber is then accelerated and shot into a mold. There, the melt solidifies to form the component which is to be produced. For the purpose of dosing the melt into the casting chamber, in particular two apparatuses are known from the prior art.
A first such dosing apparatus is constituted by a ladle, which is filled with liquid melt in particular by immersion. For this purpose, the melt may be located for example in a holding furnace. An excess of melt here can flow back into the holding furnace again for example by virtue of the ladle being tilted. In order to fill the melt into the casting chamber, the ladle is positioned over a filling opening in the casting chamber and is emptied into the same by virtue of being tilted.
A further possible way of dosing a melt into a casting chamber is constituted by a closed dosing furnace, in which the liquid melt is located. In order for a casting chamber to be filled, the interior of the dosing furnace is subjected to pressure. The melt can rise up via a riser pipe, which is located beneath a level of the melt in the furnace, and flow into a filling opening of the casting chamber, for example via a channel or a suitable device. When a desired dosing quantity has been reached, the pressure in the furnace is lowered and the filling operation in the casting chamber is thus brought to an end.
The known apparatuses and methods for filling a melt into a casting chamber have a number of disadvantages. Thus, a tapering, parabolic jet of melt forms for example when the melt is being poured out of a ladle into the casting chamber. Said jet impacts on an inner surface of the casting chamber at an uncontrollable angle. The high-level impulse when impact takes place, caused in particular by the high flow speed of the melt, can give rise, even after a short period of time, to erosion on the inner surface of the casting chamber. This wear results in a reduced service life of the casting chamber. High maintenance costs ensue. Furthermore, the high drop height of the melt between the ladle and the inner surface of the casting chamber promotes the formation of turbulence and oxides when impact takes place in the casting chamber. Such oxides, however, can have a negative effect on the properties and on the quality of the component produced.
When use is made of a dosing furnace, the quantity of melt is dosed, as described above, by way of regulation of the positive pressure in the furnace chamber. This procedure is very imprecise and can result in a dosing accuracy of up to +/−2.5%. Different quantities of melt in the casting chamber, however, have a negative effect on the quality of the component to be produced since in the case of a quantity being too low, for example the mold for the component is not completely filled and, in the case of a quantity being too large, the biscuit is unnecessarily large, and has to be melted again in an energy-intensive and costly manner. A high reject rate of the components produced and/or an increase in the production costs as a result of the melting operations which are necessary in addition ensue/ensues. Furthermore, such a dosing system, which is based on positive pressure, is very sluggish, and this has a considerable influence on the cycle time during production of the components.
It is therefore the object of the present invention to eliminate, at least in part, the above described disadvantages of known apparatuses for filling a melt into a casting chamber for die casting, and of methods for filling a melt into a casting chamber for die casting. In particular, it is the object of the present invention to provide an apparatus for filling a melt into a casting chamber for die casting, and a method for filling a melt into a casting chamber for die casting, which straightforwardly and cost-effectively improve the operation of filling a melt into a casting chamber for die casting, wherein in particular wear to the casting chamber is reduced and the quality of the component which is to be produced by the die casting is increased.
As far as a first aspect of the invention is concerned, the above object is achieved by an apparatus for filling a melt into a casting chamber for die casting according to embodiments of the invention. According to a second aspect of the invention, the object is achieved by a method for filling a melt into a casting chamber for die casting according to embodiments of the invention. Features and details here which are described in relation to an apparatus according to the invention of course also apply in relation to a method according to the invention, and vice versa, and therefore reference is or can always be made from one to the other for the disclosure relating to the individual aspects of the invention.
According to a first aspect of the invention, the object is achieved by an apparatus for filling a melt into a casting chamber for die casting, having a tundish with an inner volume, wherein the inner volume can be filled with the melt. An apparatus according to the invention is characterized in that the tundish in the casting chamber can be arranged in a reversible manner over an inner surface of the casting chamber, wherein the tundish has a pouring opening for filling the melt into the casting chamber and also a closure body for opening and closing the pouring opening.
An apparatus according to the invention is designed for filling a melt into a casting chamber for die casting. The melt used here may be, for example, molten aluminum. For this purpose, the apparatus has a tundish with an inner volume. The inner volume here can be filled with the melt. It is essential to the invention that the tundish can be arranged in the casting chamber in a reversible manner over an inner surface of the casting chamber. Arranging over the inner surface of the casting chamber, within the context of the invention, means in particular that the tundish is located, at least in part, in the interior of the casting chamber and the distance between the pouring opening of the tundish and the inner surface of the casting chamber is small. This distance, the so-called outlet gap, is preferably no more than approximately 10-200% of the diameter of the pouring opening and/or less than approximately 15 cm, preferably less than approximately 5 cm, particularly preferably less than approximately 1 cm.
This small outlet gap between the pouring opening and the inner surface of the casting chamber means that a high impact speed of the melt on the inner surface of the casting chamber when the melt is being filled into the casting chamber can be reliably avoided. Erosion on the inner surface of the casting chamber can thus be prevented and the wear to the casting chamber can be reduced overall. A longer service life of the casting chamber can thus be made possible. For the purpose of filling the melt into the casting chamber, the melt is filled beforehand into the inner volume of the tundish. It is contemplated in particular here to monitor the level of the melt in the inner volume of the tundish, for example by a suitable laser and/or ultrasound method and/or eddy-current method. Of course, it is possible here for the apparatus, in particular the tundish, to have the necessary sensors and evaluation devices. Such monitoring of the level in the inner volume can ensure, in particular, a constant quantity of melt in the inner volume of the tundish. Constant filling of the casting chamber with a constant quantity of melt can thus be made possible. On the one hand, this makes possible an increase in the quality of the component which is to be cast, and therefore a reduction in the amount of defective components rejected as a result of the quantity of melt being too small. On the other hand, the biscuit is the necessary size. The production costs of the components can thus be reduced. In particular, provision may also be made, for example, for the inner volume to have a ceramic material and/or a coated metal, in particular a metal coated with a size, at least over part of its surface. This means that all the melt can flow out into the casting chamber. A further increase in the component quality can be achieved in that, once the tundish has been arranged in the vicinity of the inner surface of the casting chamber and the pouring opening has been opened, the tundish remains in this position until all the melt has flown out of the inner volume of the tundish into the casting chamber. The pouring opening is thus below the level of the melt in the casting chamber as soon as this level rises above the outlet gap. This can avoid the situation where the melt, when it is being filled into the casting chamber, penetrates an oxide layer which forms on the surface of the melt in the casting chamber. Turbulence of this oxide layer, and the resulting distribution of this oxide layer in the melt, can thus be avoided. As a result, the purity of the melt in the casting chamber can be enhanced and consequently, in turn, the quality of the component which is to be cast can be increased. Overall, it is thus possible for an apparatus according to the invention to reduce the wear to the casting chamber used and, at the same time, to increase the quality of the die-cast components produced.
Provision may also be made, in the case of an apparatus according to the invention, for the tundish and/or the inner volume to be of funnel-like design. Funnel-like, within the context of the invention, means that the tundish and/or the inner volume are/is, of at least partially conical design. Provision may particularly preferably be made here for the funnel-like tundish to taper in the direction of the pouring opening. Such a funnel-like tundish, in particular the outer shape of the tundish being of funnel-like design, is thus at least partially conical on the outside. This shaping can act as an introduction aid and/or centering aid in a filling opening of the casting chamber. This can facilitate the operation of arranging the tundish over the inner surface of the casting chamber. As a result of a funnel-like inner volume, a melt which is located in the inner volume of the tundish can flow out to particularly good effect through the pouring opening. Provision may particularly preferably be made here for the inner volume to be of funnel-like design to the extent where an internal diameter of the inner volume tapers in the direction of the pouring opening. This makes it possible for the inner volume, when the pouring opening is open, to be emptied in a completely passive manner under the force of gravity alone, no more melt remaining in the interior of the inner volume. A particularly good dosing capability of the quantity of melt which is introduced into the casting chamber can thus be achieved.
Provision may additionally be made, in the case of an apparatus according to the invention, for the closure body to be designed in the form of a valve body for opening and closing the pouring opening, wherein the valve body, in a first position, closes the pouring opening and, in a second position, opens the pouring opening. A valve body here constitutes a particularly straightforward way of providing a closure body. It is particularly preferably possible here for the valve body to be arranged in the interior, or at least essentially in the interior, of the inner volume of the tundish. It is possible here for the valve body, in its first position, to close the pouring opening in the manner of a stopper and to be moved simply in the direction of the interior of the inner volume, into its second position, in order to free the pouring opening and thus to open. This arrangement has, in particular, the advantage that the melt, as a result of the force of gravity, subjects the valve body to a force which pushes the valve body into its first position on the pouring opening. A particularly tight closure of the pouring opening by such a valve body can thus be made possible in a particularly straightforward manner.
In a further development of an apparatus according to the invention, provision may also be made for the valve body to have a contact protrusion which projects out of the tundish, in particular out of the pouring opening, and is designed for establishing contact with the inner surface in the casting chamber, wherein, by virtue of contact being established, the valve body can be moved from its first position into its second position. This contact protrusion is designed in geometrical terms such that it can be used according to the invention, in particular that it is designed for establishing contact with the inner surface in the casting chamber. In particular, provision may be made here for the contact protrusion to project out of the tundish or of the pouring opening over a greater extent than the outlet gap, which remains between the pouring opening and the inner surface of the casting chamber when the tundish is arranged over the inner surface. The contact protrusion thus bridges said distance between the tundish and the inner surface of the casting chamber. When the tundish is arranged over the inner surface of the casting chamber, the contact protrusion thus establishes contact with the inner surface of the casting chamber even before the tundish has assumed its definitive position in the casting chamber. As a result, the valve body is pushed into the interior of the tundish and the pouring opening is thus opened automatically. This constitutes particularly straightforward opening of the pouring opening, since said opening takes place automatically when the tundish is arranged over the inner surface of the casting chamber. High-outlay control mechanisms for opening the pouring opening of the tundish can thus be avoided. An apparatus according to the invention can thus be of relatively straightforward design overall.
Furthermore, an apparatus according to the invention can be designed to provide an elastic element, in particular a spring, of which the force acts on the valve body in the direction of its first position. This elastic element therefore pushes the valve body into its first position, in which the pouring opening is closed by the valve body. In particular when there is no contact protrusion present for the inner surface of the casting chamber, the elastic element therefore causes the pouring opening to close automatically. This is advantageous, in particular, when, once the melt has been filled into the casting chamber, the tundish is removed from the latter again. Such an elastic element thus constitutes a particularly straightforward and advantageous way of providing for automatic closure of the pouring opening by way of the valve body. There is no need for any additional actuators, for example motors. A further simplification in the construction of an apparatus according to the invention can thus be made possible.
In another further development of an apparatus according to the invention, provision may also be made for the valve body, at least in part, to be of plug-shape, plate-shape or trough-shape, in particular omega-trough-shape, design. Provision may particular preferably be made here for these formations of the valve body to be arranged at that end of the valve body at which the melt can flow into the casting chamber. Provision may also, of course, be made for a sealing surface, which can be provided on the valve body for the purpose of establishing contact with a surface of the pouring opening, to correlate with said different embodiments or to be adaptable to said embodiments. The different embodiments here have different advantages. Therefore, a plug-shape configuration of a valve body allows a particularly laminar outflow of the melt into the casting chamber. Problematic turbulence in the melt can thus be avoided. A plate-shape configuration of the valve body can achieve concentric outflow of the melt into the casting chamber. The melt is distributed uniformly in the casting chamber, and this can avoid loading of the casting chamber as would occur for example when the melt impacts at certain points. A trough-shape configuration of the valve body can avoid, for example, sloshing of the melt into the casting chamber, which can be accompanied by the casting chamber being subjected to a high level of local loading. An omega-trough-shape configuration, in which the trough is shaped like the Greek letter omega, can provide in particular the outflow of the melt from the tundish with the preferred direction, which is predetermined by the opening of the omega. In particular the operation of filling an elongate casting chamber can be improved by such an at least partially directed jet of melt.
It is also possible for an apparatus according to the invention to be developed further to the extent where a valve-seat ring is arranged on the pouring opening, and where the valve body has a contact cone, in particular a contact cone of an angle of approximately 5°, for establishing contact with the valve-seat ring. It is preferable here for the valve-seat ring and/or the contact cone to taper in the direction of the first position of the valve body. In particular, provision may also be made for the valve-seat ring and the contact cone to be coordinated with one another. Particularly good sealing of the pouring opening can thus be achieved.
It is also possible for an apparatus according to the invention to be designed, in a further development, such that the valve body is mounted in a linearly movable manner in a bearing. Such a bearing for linear bearing purposes here constitutes a particularly straightforward way of fastening the valve body in a movable manner in a tundish. In particular, such a bearing can provide in a particularly straightforward manner for a linear displacement of the valve body when contact is made between the contact protrusion and the inner surface of the casting chamber. In a further development, provision may additionally be made for an appropriate helical groove and a pin, which is designed for engaging in the groove, to give rise to the linear movement being accompanied by a rotary movement of a few degrees, preferably of approximately 15° or less. It is possible here for the groove to be arranged on the valve body and for the pin to be arranged on the bearing means, or vice versa. The sealing of the pouring opening by way of the valve body can thus be improved further.
According to a particularly preferred embodiment of an apparatus according to the invention, provision may also be made for the tundish to be fixed on a casting channel, wherein the tundish can be filled via the casting channel and can be pivoted together with the casting channel in order to be arranged over the inner surface of the casting chamber. Such a casting channel means that the inner volume of the tundish can be filled particularly straightforwardly. It is also the case that the operation of arranging the tundish over the inner surface of the casting chamber can be done particularly straightforwardly in this embodiment of an apparatus according to the invention. The operation of pivoting the system made up of the tundish and casting channel can be carried out here, for example, by a straightforward shaft with a protuberance. In particular, it is preferably also conceivable for the movement of the tundish or the casting channel to be coupled to a movement of a plunger in the casting chamber, the plunger being provided for the purpose of shooting the melt into the actual mold during the actual die-casting operation. Collision of the tundish, which can be arranged in the casting chamber, and of the plunger, which moves in the casting chamber, can thus be prevented in a particularly straightforward manner.
It is preferably possible for an apparatus according to the invention to be developed to the extent where the tundish and/or casting channel are/is of closed design. Such a closed design can prevent, for example, heat losses from the melt in the inner volume or the casting channel, as a result of which the amount of energy used overall can be cut back. Furthermore, such a covering can also be used for protecting, for example, sensors which is arranged for level-measuring purposes in the interior of the inner volume.
In a further development of an apparatus according to the invention, provision may also be made for the tundish and/or the casting channel to be fillable, or filled, at least in part with an inert gas, in particular with argon. Such an inert gas can prevent, in particular, a reaction of the melt with oxygen, in particular with atmospheric oxygen. This can avoid in particular the formation of an oxide layer on the surface of the melt, as a result of which the purity of the melt, and therefore the quality of a component produced from the melt, can be improved overall.
Provision may also be made, in the case of an apparatus according to the invention, for the tundish to have an overflow opening for limiting a level of the melt in the inner volume. The level of the melt in the inner volume of the tundish can, of course, be monitored by a suitable sensor system, for example by laser sensors and/or ultrasonic sensors and/or sensors for an eddy-current method, in order to ensure a uniform quantity of melt in the inner volume. In the event of the sensor system failing, and/or if there is no such sensor system present, an overflow opening can nevertheless ensure that a certain quantity of melt is not exceeded in the inner volume. If the inner volume is filled with too much melt, this can flow out of the inner volume through the overflow opening. Of course, provision may be made here for the exiting melt to be collected outside the tundish and reused. Such an overflow opening can thus ensure a constant and/or defined quantity of melt in the inner volume of the tundish even if there is no sensor system present or in the event of a sensor system failing.
According to a second aspect of the invention, the object is achieved by a method for filling a melt into a casting chamber for die casting by way of an apparatus, in particular one having the features according to the first aspect of the invention. A method according to the invention is characterized by the following steps:
a) filling the melt into an inner volume of a tundish of the apparatus,
b) arranging the tundish over an inner surface of the casting chamber,
c) opening a pouring opening of the tundish, for the purpose of filling the melt into the casting chamber, by way of a closure body of the tundish,
d) filling the melt into the casting chamber,
e) closing the pouring opening by way of the closure body, and
f) moving the tundish away from the inner surface.
Provision may particularly preferably be made, in the case of the method according to the invention, for the method to be implemented using an apparatus according to the first aspect of the invention. All the advantages of an apparatus according to the invention, which is designed according to the first aspect of the invention, thus, of course, also apply in the case of a method according to the invention, that is implemented using such an apparatus.
In step a) of the method according to the invention, melt is filled into an inner volume of a tundish. In particular, provision may, of course, be made here for measures to be taken to ensure a constant quantity of melt in the inner volume of the tundish. In step b) of the method according to the invention, the tundish is arranged over an inner surface of the casting chamber. The tundish here is arranged over the inner surface such that an outlet gap, that is to say the distance between a pouring opening of the tundish and the inner surface of the casting chamber, is small. The outlet gap here is preferably smaller than approximately 10% to approximately 200% of a diameter of the pouring opening and/or smaller than approximately 15 cm, preferably smaller than 5 cm, particularly preferably smaller than approximately 1 cm. In step c) of the method according to the invention, a closure body of the tundish opens the pouring opening of the tundish in order to allow the melt to be filled into the casting chamber. This is carried out in step d) of the method according to the invention. The operating of filling the melt into the casting chamber in step d) takes place, in particular, preferably in a passive manner purely by way of the force of gravity acting on the melt. It is preferable here for the tundish to remain in its position over the inner surface of the casting chamber throughout the filling operation in step d). This makes it possible, at least temporarily, for the melt to be filled into the casting chamber beneath a level of the melt therein, as a result of which turbulence of any oxide layer which may be present on the surface of the melt in the casting chamber can be avoided. Following completion of the operation of filling the melt into the casting chamber, the pouring opening is closed in step e) by a movement of the closure body and then, in step f), the tundish is moved away from the inner surface of the casting chamber, in particular is moved all the way out of the casting chamber. Of course, both in steps b) and c) and in steps e) and f), it is contemplated to have at least partially simultaneous execution of the operations of moving the tundish and of opening and closing the pouring opening. A method according to the invention can therefore avoid damage to the inner surface of the casting chamber, in particular as due to erosion, in particular by providing for a small drop height of the melt between the pouring opening and said inner surface. Using the tundish can also achieve a constant quantity of melt for the casting chamber. Overall, it is thus possible for the operation of filling a casting chamber with melt to be simplified, accelerated and rendered more cost-effective.
Provision may also be made, in the case of a method according to the invention, for, in step a), a level of the melt in the inner volume to be monitored, preferably by a laser-measuring method and/or an ultrasonic-measuring method and/or an eddy-current method, in order to determine a quantity of the melt in the inner volume, wherein deposits in the inner volume are taken into account in particular during the operation of determining the quantity. It is, of course, possible here for an apparatus which is designed for implementing a method according to the invention to have the necessary sensor system, for example laser sensors and/or ultrasonic sensors and/or sensors for an eddy-current method, and the evaluation means which are necessary for evaluating purposes. Monitoring the level of the melt in the inner volume, in particular with additional account being taken of deposits in the inner volume, means that a constant quantity of melt in the inner volume, and thus in the casting chamber, can be achieved in a particularly straightforward manner. A particularly effective filling operation in the casting chamber with precisely the correct quantity of melt can thus be achieved in a particularly straightforward and in particular reproducible manner.
It is also possible for a method according to the invention to be developed further to the extent where the tundish, in particular the inner volume, and/or a casting channel, are/is heated, and/or where the tundish, in particular the inner volume, is cleaned prior to step a). Heating of the tundish, in particular the inner volume, can prevent deposits of the melt in the inner volume, since the melt can always be kept in a liquid state by the heating. Deposits which may nevertheless be present can be removed from the tundish, in particular from the inner volume, and/or the casting channel by cleaning. Both measures therefore provide for a deposit-free inner volume, as a result of which a constant quantity of melt in the inner volume can be ensured in a particularly straightforward manner.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.